Note: Descriptions are shown in the official language in which they were submitted.
1175520
ELECTRIC TERMINALS h~Vl~lG Pl ATED INTE~lOr~ SIJF~FACES, ~PPAP~TU'`
FOR AND hlFTI-10~ OF SELECl-IVEI Y PLATING SAlr~ TEF~ ',lNAL~
The present invention relatcs to selective platin~, i.e., elec~roplatin~
selectively only the electrical contact surfaces of electrical terminals to th~e
exclusion of other surfaces of the terminals and, in particular, termin7;1s
that are attached to a carrier strip.
In one method of manufacturinc; electrical terminals, the terrr:inals arc
starnped and forlned from metal strip and are attached to a carrier strip.
This carrier strip is useful ~or strip feeding t11e ter~inals through
successive manufacturing operations. One necessary rlanufacturillcl
operatiorl involves plating, i.e., electroplatirlg the el~ctrical contact
surfaces oF the strip Fed terminals with a contact rnetal, usually noble
metals or noble rnetal alloys. These metals are characteri~ecl l~y sood
electrical conductivity allcl little or no formation of oxides that redl!ce the
conductivity~ Theref(lre, these metals, when applied as ,~ latincJ, will
enhance conductivity of the terminals. The llicJIl cost oF these r,letals has
necessitated precision deposition on the contact surfaces of the te rminals,
and not on surfaces of the terminals on which plating is unnecessary.
Apparatus for plating is called a platin~ cell and includes an electrical
anode, an electrical catho{le comprisec3 of the strip fed terrlillal~" and a
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plating solution, i.e., an electrolyte of metal ions. A strip
feeding means feeds the strip to a strip guide. The strip guide
guides the terminals through a plating zone while the terminals
are being plated. The plating solution is fluidic and is placed
in contact with the anode and the terminals. The apparatus
operates by passing electrical current from the anode through the
plating solution to the terminals. The metal ions deposit as
metal plating on those terminal surfaces in contact with the
plating solution.
There is disclosed in United States Patent No. 3,951,761,
plating apparatus in which strip fed terminals are plated by
i~lmersion in a plating solution. The carrier strip is masked,
i.e., covered by a conductive strip, that prevents deposition of
plating onto the immersed carrier strip. However, masking
requires another manufacturing operation. Some immersed surfaces
are difficult to mask, particularly the surfaces of small size
electrical terminals. The present invention accomplishes
selective plating according to a rapid automatic process and
apparatus without a need for masking immersed terminal surfaces
on which plating is unnecessary. The present invention is
particularly adapted for plating only interior surfaces of strip
fed, receptacle type, terminals, and not the external surfaces,
despite contact of the external surfaces with plating solution.
In accordance with a first broad aspect, the present
invention provides a method for plating interior surfaces of
electrical terminals that are spaced apart and attached to a
carrier strip comprising feeding the strip from a supply reel to
a strip guide which guides the terminals through a plating zone
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while they are being plated, supplying an electrolytic plating
solution to the plating zone, bringing the terminals in the
plating zone in close proximity to an anode, and supplying an
electrical flow from the anode, through the plating solution to
a cathode, the method being characterized in that anode extensions
enter the interiors of the terminals as the terminals move into
the plating zone, streams of plating solution are pumped through
the nozzles and over the anode extensions, as the electrical
current flows from the anode extensions, through the plating
solution to the cathode, the interior of the terminals are plated,
the anode extensions are withdrawn from the interiors of the
terminals as the terminals move out of the plating zone.
In accordance with another broad aspect thereof, this
invention is further directed to a series of electrical terminals
spaced apart and attached to a carrier strip that have selective
plating on their interior surfaces. The terminals are character-
ized in that the interior surfaces of each terminal have a
deposit of contact metal plated over a base metal, the interior
plated deposit having a thickness in excess of 0.38 microns.
Edge margins of the interior plated deposit are of tapered thick-
ness and cover at least portions of the sheared edges of the
blank which were sheared by
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stamping. The external surfaces of each terminal are substantially free of
the contact metal plating. The plated deposit is electrodeposited on the
interior surface of each terminal by an anode extension positioned within
the terminal.
A better understanding of the invention is obtained by way of
example from the following description and the accompanying drawings,
wherein:
FIGURE 1 is a perspective view of apparatus for continuous plating
according to the invention with parts of the apparatus exploded.
FIGURE 2 is a perspective view of the apparatus shown in Figure 1
with pa rts assembled .
FIGURE 2A is a schematic view of the apparatus shown in Figure 2
combined with a belt mechanism.
FIGURE 3 is an enlarged fragmentary perspective view of a portion of
the apparatus shown in Figure 2.
FIGURE 4 is a view in section of a plating cell apparatus
incorporating the apparatus of Figure 2.
FIGURE 5 is a fragmentary plan view, taken along the line 5-5 of
Figure 4, of a portion of the apparatus shown in Figure 4, and illustrating
an advanced anode extension.
FIGURE 6 is a view similar to Figure 5, illustrating a retracted anode
extension
FIGURE 7 is a perspective view of a shaft of the apparatus shown in
Figure 2.
FIGURE 8 is a section v iew of the shaft shown in Figure 7.
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FIGURE 9 is a perspective view of a vacuum aspirator of the
apparatus shown in Figure 2.
FIGURE 10 is an elevation view of an anode extension of the
apparatus shown in Figure 2.
FIGURE 11 is an elevation view in section of a portion of an electrical
receptacle that has been immersion plated.
FIGUR-E 12 is an elevation view in section of an electrical receptacle
that has been plated according to the present invention.
FIGURE 13 is an exploded view of an alternative embodiment of this
invention .
FIGURE 14 is an enlarged fragmentary perspective view of a portion
of an alternative embodiment of the apparatus shown in Figure 2.
FIGURE 14A is a plan view of a terminal having a contact slot
receptacle showing the side of the terminal that faces the mandrel.
FIGURE 15 is a view in section of a plating cell apparatus
incorporating the alternative embodiment of Figure 13 in the apparatus of
Figure 2.
FIGURE 16 is a fragmentary plan view taken along the line 16-16 of
Figure 15, and illustrating an anode extension-spreader aligned to enter
the terminal.
FIGURE 17 is a view similar to Figure 16, illustrating an advanced
anode extension-spreader.
FIGURE 18 is a perspective view of the shaft of the apparatus shown
in Figure 15, illustrating the asymmetric cam used to advance and retract
the anode extension-spreaders.
FIGURE 19 is a section view of the shaft shown in Figure 18.
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F~ P~ 20 iS ?n enlarcJecl fragmentary perspective vicw of the
alternati\~e embodin)el~t of Fi~3ure 13 illustratin~3 th~ oper-tion of the
a syr,~metrical cal,.
FIGURE 21 is an enlarged fra~mentary view of an eiectrical terminal
that has been plated according to the alternative embocliment of the
present i nvention .
Figures 1, 2, and 4 illustrate a mandrel apparatus 1 according to one
embodiment of the invention comprising an assenlbly of an insulative disc
flan~e 2, an insulative wheel-shaped mandrel 3, an insulative nozzle plate
4, a conductive titanium anode plate 5, a conductive copper--grapllite
bushincJ 6 that is attached to the anode plate 5, an insulative anode
extension holder plate 7, an insulative hydraulic distributor plate 8, a
shaft 9, an end cap 10 for fitting on the end of the shaft S, a washer 11
and a sealing ring 12 compressed between the disc flange 2 and the er1d
cap 10. The insulative parts 2, 3, 4, 7, and 8 are adva1lta~3eously
machined from a high density polyvinylchloride, ancl are stackecl ~ogether
with the conductive parts 5 ancl 6. ~olts 13 are assembled throuqh
aligned bolt receiving holes 14 through each of the parts 2, 3, 1~, 5, 7,
and 8. These parts are mountec! for rotation on t'ne shaft 9. A
continuous lenqtll of strip fed electrical terminals 15 are intcgra' with, anc'
serially spaced alollcJ~ a carrier strip 16. The terminals 15 are sho~ n as
electrical receptacles of barrel forms or sleeve forms. These forms are
exemplary only, since many forms of electrical receptacles exist. The
strip fed terminals 15 are shown in Figure 2A as being looped ever two
idler pulleys 17 and or-to a cylindrical alignment surface 1~, of the rnandrel
3.
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Figure 3 shows a series of radially projectin~ t eth 19 in~egral with
and projectin~ from the ali~nment surfclce 18. The terminals 15 are nested
in the s~. cej that form nes~s 20 ~-etWc n ;he teeth 1;~. The carrier strip
15 has pilot holes 21 in which are rec~istered knobs 22 projecting from the
mandrel 3. The flange 2 provides a rim projectin~; agair)st and along the
carrier strip 16. Figure 2A illustrates a belt looped over the pul:eys 17
and also over two additional pulleys 25. The belt 24 also is held by the
pulleys ,25 against the terminals 15 that are nested in the nests 20 and
the belt retains these terminals 15 against the alk~tlment surface 18 of the
mandrel 3. Thereby the stripped terminals 15 are between the be't 24 and
the alignment surface 1~ whereas the belt 24 is between the strip ~ec!
terminals and the pulleys 17.
Figure 3 shows a nozzle wheel 4 that is turreted with a pluratity of
radial!y spaced orifices or nozzles 26. Fi~3ul-es 1 and 4 show that th~
nozzles 26 are aligned with anc' open into the nes.s 2~J. Anode exterlcions
29 are mounted within the no~zles 2fi. Tl-ese ficJures also show th~ anc~e
plate 5 that includes a plurality of rac~ially spaceci anode extcrlsinn
receivin~3 openings 27 that are ali~ned with and open into the r ozzle
openings 26. The anocle extension holder plate 7 includes a plurality Or
anode extension receiving charnbers 28 aligned with alld cornm-!nicating with
the openings 27 in thé anode plate 5.
Figure 10 shows an anode extension 29 machined from ~ conductiv
metal such as titanium. The anode extension has an enlarged diameter
body 30 and a reduced diameter elongated probe 31 integral Wit51 the body
30. A section of the probe 31 is fabricated ol a coil spring 31A which
makes a probe flexible. A radially projectin~ insulative collar 32 is
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mountecl on th~ tip of the probe 31. One or rnore flat pass2~eways 33 are
recessec~ in the periphery of the body 30 and extend !ongitudinally fro~n
one erd of the body to the o-~her.
As shown in Figures 4, 5, and 6 an znode extension body 30 is
mounted for reciprocation in each chamber 28. The probe 31 of each
anode extension body 30 projects into the openings 27 26 that are aligned
with the respective chamber 28. The ali~3ned openings 27 26 together
with the chambers 28 cooperate to form anode extension passaseways that
mount the anode extensions 29 for reciprocation. The probe 31 of each
anode extension 29 is mounted for advance into an interior of a terminàl
15, as shown in Figure 5, and also for retraction out of an interior of a
terminal 15, as shown in Figure 6. As each anode e.Ytension 29 is
advanced into an interior of a terminal 15, the bocly 30 of the anod~
extension will impinse and stop a~ainst the anode plate 5, providing a
electrical connection therebetween.
Figures 1 and 4 show that the distributor plate 8 includes a centr21
opening 34 communicating with a plurality of electrulyte passageways 35
that extend radially outward of the opening 34 and comrnunicate with
respective anode extension chaml~ers 28.
Figures 7 and 8 show the shaft 9 that is made of c¢nductive stainless
steel. The shaft 9 is provided with a central stepped cylindrical
electrolyte conduit 36 extending entirely the length of the shaft. A
plurality of electrolyte ports 37 connect the conduit 36 with a
channel-shaped electrolyte inlet manifold 38 recessed in the cylindrical
periphery of the shaft. A plurality of vacuum ports 39 connect the
conduit with a channel-shaped vacuum manifold L~0 that is recessed in the
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cylindrical periphery of the shaft 9, so that the central o?ening 34 of the
plate 8 communicates with the manifolds 38, 40. The electrolyte
passageways 35 that extend to the central opening 3~ will c/,mmullicate ~ h
the eiectrolyte inlet manifold 38, and then the vacuum marifold 40, in
turn, as the distributor plate 8 is rotated relative to the shaft 9.
Figure 9, taken with Figures 4 and 8, show a vacuum aspirator 41
machined from polyvinylchloride. The aspirator 41 is seated in the conduit
36 of the shaft 9. One or more longitudinal electrolyte passageways 42 are
recessed in the periphery of the aspirator 41 and permit electrolyte flow
along the conduit 36 into the ports 35 and the electrolyte inlet manifold 38.
A longitudinal bore 43 through the aspirator 41 permits additional
electrolyte flow throu~3h the aspirator 41, to the end Or the conduit 36,
through a passageway 44 through the end cap 10, and out a conduit 45
that is attachec! to the end cap 10 and communicates with the cap
passageway 44. A series of vacuum ports 46 through tile aspirator
intercept the bore 43 . The vacuum ports 46 communicate w i~h the vacuum
ports 39 and with the vacuum manifold 40. The electrolyte flow along the
bore produces a vacuum in the vacuum ports 46 and also in the vacuum
manifold 40. This phenomenon is well known in the art of hydraulic f!uid
devices .
Figure 4 shows schematically a plating cell, including a source E of
electrical pGtential applied across the strip 16 and the ano(le plate 5, a
tank 47 containin~ a plating electrolyte 48 of precious or semi-precious
metal ions and a supply hose 49 leading from the tank 47 through a pump
50 and into the conduit 36 of shaft 9. A drive sprocket with an axle
bushing is secured on the clistributor plate 8.
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In operation, the sprocket is driven by a chain drive (not shown) to
rotate the mandrel apparatus 1 and to feed the strip fed terminals 15 upon
the mandrel 3. ~lectrolyte 48 is supplied under pressure from the hose 49
into the conduit 36 of the shaft 9. An electrical potential from the source
E is applied between the anode plate 5 and the strip fed terminals 15 to
produce a current 1. The terminals 15 serve as a cathode onto which
precious or semi-precious metal ions of the electrolyte 48 are to be plated.
Upon rotation of the mandrel 3, each of the anode extension chambers 28,
in turn, will communicate with the electrolyte manifold 38. The electrolyte
will flow under pressure into the electrolyte manifold 38, and from there
into several of the anode extension chambers 28 that communicate with the
electrolyte manifold 38. The anode extensions 29 in these anode extension
chambers 28 will be advanced to positions as shown in Figure 5 by the
electrolyte under pressure. Electrolyte will flow past the anode extension
bodies 30 along the anode extension passageways 33, and be injected by
the nozzles 26 into the interiors of the terminals 15, wetting the terminal
interiors and the anode extension probes 31 which are in the terminal
interiors. Sufficient ion density and current density are present for the
ions to deposit as plating upon the surfaces of the terminal interiors. The
proximity of the probes 31 to the terminal interiors assures that the
surfaces of the terminal interiors are plated, to the exclusion of the other
terminal surfaces. The collars 32 on the anode extensions are sized nearly
to the diameters of the interiors of the terminals to position the anode
extension probe precisely along the central axis of the terminal interiors
during the plating operation.
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ll~SSZO
As the mandrel apparatus 1 is further rotated, the anode extcnsion
chambers 2~ will become disconnected from the electrolyte manifold 38, and
will become connected with the vacuum manhold 40. The vacuum pre:,ent
in the vacuum manifold 40 will tend to draw out residual electrolyte in the
several anode extension chambers 28 that communicate with the vacuum
manifold 40. The vacuum also will retract the anode extensions 29 fror:
their advanced positions, as shown in Figure 5, to their retracted
positions, shown in Figure 6. Thereby the probes 31 become withdrawn
from the interiors of the terminals 15, plating deposition will cease, and
the terminals hecome removed from the mandrel apparatus 1 as the strip 6
continues to be advanced.
Figures 13 and 15 illustrate a mandrel apparatus 1 ' according .o an
alternative embodiment of the invention comprising an assembly of an
insulative bearing case 54, a two-piece insulative disc flarge 2', an
insulative wheel-shaped mandrel 3', an anode extension-spreader retaining
ring 56, and a conductive shaft 9'. Bolts 13' are assemhled through
aligned bolt receiving holes 14' through each of the parts 54, 2', and 3'.
These parts are mounted for rotation on the shaft 9'. A continuous length
of strip fed electrical terminals 15' are integral with, and serially spaced
along, a carrier strip 16'. The strip fed terminals 15' are strip fed to the
apparatus 1 ' in the same manner as are the strip fed terminals 5 as shown
in Figure 2A.
This embodiment of the invention is used with electrical terminals
having contact slot receptacles of the type shown in Figure 14A. In order
to plate inside a siotted terminal, according to the invention, the slot first
must be spreacl apart to permit insertion of the anode extension. As is
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illustrated in Figures 13 and 14, anode extension-spreaders 29' are used in
this embodiment. The anode extension-spreaders 29' are inserted
essentially at right angles to the terminais 15'. Figure 14 shows that each
anode extension-spreader 29' is comprised of a conductive metal strip 60
and a plastic spreader body 62. The metal strip 60 extends below the
plastic spreader. The plastic spreader body 62 has a retaining slot 64
along its upper edge which cooperates with the anode extension-spreader
retaining ring 56. The anode extension-spreader is shaped at its
outermost end 66 to spread and fit within the terminals 15' and to properly
position the metal anode portion inside the terminal. `
Fi~3ure 14 shows that mandrel 3' is turreted with a plurality of
radially spaced anode extension-spreader passageways 58 which extend
outwardly to the alignment surface 18' and form a series of nests 20' along
the periphery mandrel 3'. The terminals lS' are held in these nests and
against the mandrel as the terminals are plated internally.
Figure 14 further shows that mandrel 3' is turreted with a plurality
of radially spaced orifices or nozzles 26' at the base of the anode
extension-spreader passageways 58. When the anode extension-spreaders
29' are placed in the mandrel, the metal strips 60 lie within the noz-zles
26' .
As shown in Figures 14, 15, 16, and 17, the anode
extension-spreader 29' is mounted for reciprocation in each passageway 58.
The shaped end 66 of each anode extension-spreader is r!lounted for
advancing into the slot of a terminal 15' as shown in Figure t6. Figure 17
shows the advanced anode extension-spreader in the terminal 15'. As each
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anode extension-spreacler 2~' is advanced it is held in contact with the
conductive shaft 9', providing an electrical connection therebetween.
Fisures l S, 18 and 19 show the conductive shaft 9~ is provided with a
central cylindrical electrolyte conduit 36' extending along part of the
length of the shaft. A channel-shaped electrolyte outlet 68 is recessed in
the cylindrical periphery of the shaft 9'. As the mandrel 3' revolves
about shaft 9', the nozzles 26' communicate with the electrolyte outlet 68
thus providing access of the electrolyte solution to the terminal 15'.
Figures 15, 18 and 19 show the asymmetric cam 70 on the shaft 9'.
The shape of cam 70 can be seen in Figure 20. Mandrel 3' has a circular
opening 72 at its center which is dimensioned to closely fit and cooperate
with shaft 9'. The cam 70 fits into a circular opening 72 on the side of
mandrel 3' having the anode extension-spreader passageways S8.
Approximately half of cam 70 fits snugly against passageways 58 while the
other part of cam 70 is spaced apart from passageways 58. The inner
ends 74 of anode extension-spreaders 29' are held snugly against cam 70
by the anode extension-spreader retaining ring 56.
As mandrel 3' rotates around shaft 9', the anode extension-spreaders
29' are first extended into the terminals 15' as cam 70 moves against
passageways 5~ and then retracted from terminals 15' where the cam is
spaced apart from said passageways.
Fisure 15 shows schematically the mandrel apparatus, including a
source E of electrical potential applied across the strip 16 and the
conductive shaft 9'. A drive sprocket with an axle bushing is secured to
the mandrel 3'.
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In operation, the sprocket is clriven by a chain drive ( not shown) to
rotate the mandrel apparatus 1 ' and to feed the strip fed terminals 15'
upon the mandrel 3'. Electrolyte 48' is supplied under pressure from a
plating bath (not shown) into the conduit 36' of the shaft 9'. An
electrical potential from the source E is applied between the shaft 9' and
the strip fed terminals 15' to produce a current 1. The terminals 15'
serve as a cathode onto which precious or semi-precious metal ions of the
electrolyte 48' are to be plated. Upon rotation of the mandrel 3', each of
the nozzles 26', in turn, will communicate with the electrolyte outlet 68.
The electrolyte will flow under pressure into the electrolyte outlet 68, ahd
from there into several of the nozzles 26' that communicate with the
electrolyte outlet 68. The anode extensions 29' in these anode
extension-spreader passageways 58 will be advanced to positions as shown
in Figure 17 by action of the asymmetric cam 70. Electrolyte will flow past
the metal portion anode extension-spreader 29' into the interiors of the
terminals 15', wetting the terminal interiors and the portion of the anode
extensions which are in the terminal interiors. Sufficient ion density and
current density are present for the ions to deposit as plating upon the
surfaces of the term7nal interiors. The proximity of the anode
extension-spreader end 66 to the terminal interiors assures that the
surfaces of the terminal interiors are plated to the exclusion of the other
terminal surfaces. Excess electrolyte will flow past the anode
extension-spreader and will be returned to the plating bath (not shown).
As the mandrel apparatus 1 ' is further rotated, the pàssageways 58
will become disconnected from the electrolyte outlet 68. The action of cam
70 will cause the anode extension-spreaders to withdraw from the interiors
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of the terminals 15', and plating deposition will cease. The terminals
become removed from the mandrel apparatus 1 ' as the strip 16' continues to
advance .
In this alternative embodiment 1 ' of the mandrel apparatus, the use of
mechanical means to reciprocally move the anode extension-spreaders into
and out of the terminals eliminates a number of parts that are necessary
for the hydraulically operated mechanism to provide reciprocating
movement. Mechanical means can also be used with mandrel apparatus 1.
The use of anode extension-spreaders inserted at right angles to the
terminals instead of a straight line insertion also reduces the number of
parts required ~or the mandrel apparatus.
Because the slots in the terminals used in embodiment 1 ' must be
spread apart to permit insertion of the anode extension, the anode
extension-spreaders do become worn after a period of time. Depending
upon the type of plastic used, over 25,000 insertions per anode
extension-spreader can be made before replacement is necessary. The
worn anode extension-spreaders are designed to be disposable and are
easily replaced by removing bolts 13 and separating the three main pieces.
The anode extension-spreader retaining ring is then removed and new
anode extension-spreaders inserted. Flange 2' is made in two parts to
facilitate replacement of the anode extension-spreader retaining ring.
The present invention relates additionally to an electrical terminal that
has an interior with a contact metal deposit applied by the apparatus
described in conjunction with Figures 1 through 10 or Figures 13 through
20. The deposit has observable characteristics that distinguish from
characteristics of plating applied by apparatus and a process other than
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that described in conjunction with Figures 1 through 10 or Figures 13
through 20. A standard requirement of the electrical industry is that an
electrical receptacle of base metal, copper or its al'oy, should be plated
first with nickel or its alloy, then have its interior plated with a precious
or semi-precious metal such as cobalt-gold alloy that assures electrical
conductivity. Further, the plating must equal or exceed a specified
thickness that allows for wear removal of the layer by abrasion. For
example, one standard specification requires 0.38 microns thickness of
cobalt-gold plating extending from the end of the receptacle to a depth of
0.51 centimeters within the receptacle interior. The exterior surfaces of
the receptacle are not subject to wear removal. Therefore, only a flash,
i.e., 0.13 microns in thickness, of plating is required.
The deposit of noble metal or noble metal alloy may also be comprised
of successive layers of noble metals such as gold, palladium, platinum,
silver, or their alloys. Successive layers of different noble metals may
also be plated on one another, such as an under-layer of palladium
followed by an over-layer of gold.
Heretofore, plating of electrical receptacles was accomplished by the
prior processes of plating over a strip of base metal prior to forming the
strip into receptacle configurations, or by immersing fully formed electrical
receptacles in plating electrolyte and plating all the surfaces of the
receptacles. Each of these prior processes had disadvantages.
Forming a base metal strip subsequent to plating applies bending
stresses in the plating. Observation by a microscope would reveal stress
cracks in the surface of the outer plating layer. The cracks would be
most prevalent in the areas of most severe bending. Severe bending also
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would cause localized separations of the outer pla.ing layer from the metal
underlying the outer plating layer. These separations, called occlusions,
would be obse, ved by microscopic observation of a cross-section of the
outer plating layer and the underlying metal. These stress cracks and
occlusions are defects that would permit corrosion of the underlying base
metal and would be adverse to quality of the outer plating layer.
Further, stamping of the plated base metal produces shears through the
plating layers, exposing the base metal underlying the plating.
Figure 11 depicts a cross-section of an electrical receptacle plated
with a layer of nickel 51, and then immersion plated in cobalt-gold~
electrolyte, using an anode external to the receptacle during plating.
Both the interior and the exterior of the receptacle receive plating deposit
5~. The deposit on the interior rapidly tapers in thickness from the end
of the receptacle toward the innermost depth of the receptacle. For
example, the thickness varies from 0.51 microns at the end of the
receptacle to zero thickness at a depth of 0.36 centimeters from the end of
the receptacle. This tapered characteristic results from the progressive
exponential decrease in charge density or current density due to distance
from the external anode. So that thinner portions of the tapered deposit
will meet the requirement for minimum thickness, other portions of the
deposit must have excess thickness that wastefully consumes the plating
ions of the electrolyte. Since the exterior of the receptacle is relatively
near the external anode, the deposit is thicker than the deposit on the
receptacle interior. For example, the deposit has a thickness of 1.1
microns at a depth of 0 . 05 centimeters and a thickness of 0 . 51 microns at
a depth of 0.36 centimeters. Deposit on the exterior of the receptacle is
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not subjected to wear removal. Therefore, any plating in excess of a
flash, i . e., approximately 0 .13 microns in thickness, is wasted
consumption. Maskins, i.e., covering, the receptacle exterior during
plating will eliminatè the exterior deposit. However, masking requires an
operation prior to plating and is not conducive to a mass production
process. Further, masking does not eliminate wasteful consumption of a
tapered deposit on the interior of the receptacle. Upon removal of the
masking, an abrupt, not tapered, edge of the plating would be observed
where the plating had met the masking.
In the receptacle 15 of the present invention, shown in Figure 12,
the terminal is stamped and formed from a base metal of copper or its
alloy. A layer of nickel or its alloy is plated over all surfaces of the
terminal, including the sheared edges produced during the stamping and
forming operations. Using the apparatus as described in conjunction with
Figures 1 through 10, the interior is plated with an outer layer 76 of a
precious or semi-precious metal such as gold, platinum, palladium or
silver, or the alloys thereof, such as cobalt-gold. For example, an outer
Iayer of plating in the form of cobalt-gold of relatively even thickness is
deposited along the length extending from the end of the receptacle to a
distance of 0.51 centimeters toward the innermost depth of the interior.
An abrupt and steep taper is at the edges of the plating. There is an
absence of cobalt-gold, of equal or greater thickness, on the receptacle
exterior. The even thickness and abrupt tapered edges are characteristics
of the plating deposit achieved by' selective plating according to the
invention. The length of the plating deposit substantially is equal to the
length of the anode extension probe 31 that extends within the receptacle
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interior. At the terminal end of the probe 31, the charge and current
densities abruptly cease, causing an abrupt tapered edge of the plating
deposit. The charge and current densities also cease at the chamfered
end of the receptacle, causing an abrupt tapered edge of the plating
deposit. There is no need for masking the receptacle exterior, and the
plating deposit does not have the non-tapered edge that would result from
masking. Further, the plating deposit is substantially free of stress
cracks and occlusions, and has a grain structure characteristic of plating
deposit.
Figure 21 shows a receptacle 15' plated, using the apparatus as
described in conjunction with Figures 13 through 20. The plating deposit
76' on the interior surface of 15' has the same characteristics as the
plating 76 on terminal 15 as shown in Figure 12.
The invention has been described by way of examples only. Other
forms of the invention are to be covered by the spirit and scope of the
claims. The receptacles 15 and 15' are only exemplary of the many forms
of electrical receptacles, the internal surfaces of which are capable of
being plated by the apparatus of the invention.
